Medical professionals commonly use catheters for gaining prolonged access to an area within the body. Once the catheter tip is positioned at the target location, treatments such as antibiotics, chemotherapy, pain medicine, and nutrition can be administered. However, if the catheter tip is improperly positioned during insertion, or if the catheter tip migrates out of position after insertion, various risks arise, including a fluid infusion that causes pain or injury to the patient, complications due to increased thrombosis rates, delays in therapy, catheter malfunction and additional costs.
The general standard for proper catheter insertion depends on the type of catheter and the type of treatment. For example, peripherally inserted central catheters (or PICC lines) are commonly inserted into a brachial, cephalic or basilic vein in the arm and advanced through the venous system towards the superior vena cava. Current medical standards recommended that the distal tip of the catheter terminate in the lower ⅓ of the superior vena cava, close to the junction of the superior vena cava and the right atrium. However, since PICCs are commonly inserted into a vein in the arm and advanced through the venous system to reach the superior vena cava, the PICC line tip may be inadvertently positioned in a non-target area, such as the internal jugular or subclavian vein. Further, even if a PICC is property inserted, the catheter tip could later shift out of position if for example the patient coughs violently, moves a lot, or experiences severe vomiting. Therefore, verifying that the catheter tip is in the correct location is essential for safe operation of the catheter.
Catheter tip location techniques have improved the ability of medical professionals to verify the location of the catheter tip. One technique uses fluoroscopy to confirm tip location. Fluoroscopy provides the operator with real-time images of the patient's anatomy using a fluoroscope. Another technique uses electromagnetic detection and a stylet having an electromagnetic sensor placed inside the lumen of the catheter tip. Electromagnetic systems use an external device positioned directly over the internal target area for generating a magnetic field outside of the body. The electromagnetic sensor on the stylet is then inserted into the body through the catheter lumen and measures when the magnetic flux is at its greatest. A monitor indicates to the user when the electromagnetic sensor on the stylet is centered underneath the external device. In a variation of this technique, the external device senses the electromagnetic field, and an element at the tip of the stylet generates the electromagnetic field. Another technique uses ultrasound for guidance and determining catheter tip location. Electrocardiogram technology is also used determine catheter tip location by measuring the change of the P wave as the catheter progresses down the superior vena cava.
However, the systems and techniques described above have numerous deficiencies. Fluoroscopy requires a facility with fluoroscopy machine, and poses x-ray risks for both the patient and the operator. Further, interpreting the image in fluoroscopy and ultrasound can be difficult, and requires special training. Electromagnetic detection requires a stylet having an electromagnetic detecting or emitting component, and measurement accuracy can be disrupted by electromagnetic interference. Further, for patients with pacemakers or skin disorders, or for patients that are obese, device operability may dramatically decrease or be contraindicated. Electrocardiogram detection requires a normal sinus rhythm, and cannot indicate when the catheter tip is in locations including the jugular vein and the subclavian. Additionally, the technology associated with the tip location systems mentioned above can be cost prohibitive, decreasing the number of facilities properly equipped to perform catheter insertion and maintenance procedures.
Therefore, a new method of locating a catheter tip within a human body is desired in order to overcome or minimize the deficiencies described above.